Implantation of artificial lenses into the human eye has been a standard technique for many years, both to replace the natural crystalline lens (aphakic eye) and to supplement and correct refractive errors of the natural lens (phakic eye). However, accommodation provided by such replacement lenses is minimal or non-existent.
The human eye includes an anterior chamber between the cornea and iris, a posterior chamber, defined by a capsular bag containing a crystalline lens, a ciliary muscle, a vitreous chamber behind the lens containing the vitreous humor, and a retina at the rear of this chamber. The human eye has a natural accommodation ability. The contraction and relaxation of the ciliary muscle provides the eye with near and distant vision, respectively. This ciliary muscle action shapes the natural crystalline lens to the appropriate optical configuration for focusing light rays entering the eye on the retina.
After the natural crystalline lens is removed, for example, because of cataract or other condition, a conventional, monofocal IOL can be placed in the posterior chamber. Such a conventional IOL provides very limited, if any, accommodation. However, the wearer of such an IOL continues to require the ability to view both near and distant objects. Corrective spectacles may be employed as a useful solution. Recently, multifocal IOLs, defractive or refractive, divide light entering the eye and have been used to provide near and distant vision correction. Though they do provide some accommodation, they decrease contrast sensitivity and cause photopic problems such as glare and halos.
Examples of implantable intraocular lenses include various design configurations without providing significant accommodation. Generally, the lenses are attached in some manner to the eye, usually by the use of sutures or some other supporting means, such as arms or haptics, extending from the optical lens portion of the intraocular lens.
U.S. Pat. No. 6,241,777 describes a phakic intraocular lens assembly that has a lens with a circumferential edge, and a first haptic and a second haptic, which extend from the edge of the lens. Each of the haptics has a first leg extending from the lens edge to a distal end, and a second leg extending from the lens edge to a distal end, and a transverse member extending between the distal ends of each first and second leg. The transverse member can be substantially straight or bowed inward toward the lens. Each leg has a footplate at its distal end.
U.S. Pat. No. 6,261,321 (Continuation-in-part of U.S. Pat. No. 6,241,777) describes a phakic or aphakic intraocular lens assembly that has a lens with a circumferential edge, and a first haptic and a second haptic, which extend from the edge of the lens. Each of the haptics has a first leg extending from the lens edge to a distal end, and a second leg extending from the lens edge to a distal end, and a transverse member extending between the distal ends of each first and second leg. The transverse member can be substantially straight or bowed inward toward the lens. Each leg has a footplate at its distal end. Each leg of each haptic may be inwardly bowing, straight, and outwardly bowing. Additionally, each leg may have the same or different shape from the other legs.
U.S. Pat. No. 6,015,435 describes a self-centering phakic intraocular lens inserted in to the posterior chamber lens for the correction of myopia, hyperopia, astigmatism, and presbyopia. Haptic bodies are attached to optical body and extend outward from tangent points at the edge of lens in at least two generally opposite directions. Protruding surfaces protrude into pupil such that the iris interferes slightly with lens movement and provides the centering force to keep lens in place.
U.S. Pat. No. 5,133,747 describes an intraocular lens device that is partially or completely within the anterior capsular surface of the human crystalline lens. In one embodiment, the optic body has asymmetrical haptics extending outwardly from opposite sides of the circumferential edge of the optic body. In one embodiment, “J” shaped haptics extend from the circumferential edge of the optic body in a manner that encircles optic body. In another configuration, the haptics extend tangentially away from body, then reverse direction, giving the device an overall “S” shape with the lens at center portion of the S. The device is secured in place with an adhesive.
Attempts have been made to provide IOLs with accommodation, using movement along the optical axis of the eye as an alternative to shape changing. Examples of such attempts are set forth in Levy U.S. Pat. No. 4,409,691 and several patents to Cumming, including U.S. Pat. Nos. 5,674,282 and 5,496,366. These lenses are biased to be located in the posterior-most position in the eye under rest or resting conditions. When near focus is desired, the ciliary muscle contracts and the lens moves forwardly (positive accommodation). In the absence of ciliary muscle contraction, the lens moves rearward to its posterior-most resting position. Because of this posterior bias and the configuration of the lens, the posterior wall of the capsular bag is subjected to a substantial degree of stretching when the lens is in the posterior-most position. One problem that exists with such IOLs is that they often cannot move sufficiently to obtain the desired accommodation.
Therefore, it would be advantageous to provide IOLs which can achieve an acceptable amount of accommodation with reduced risk of damaging the capsular bag.